Hi @jhansome
It may be a faulty fan e.g. worn bearing or simply covered in dust causing it to not operate properly.
Here's the [https://dl.dell.com/content/manual19444273-inspiron-15-5000-service-manual.pdf?language=en-us&ps=true|service manual] for the laptop.
Go to p.51 to view the pre-requisite steps and then the procedure to remove the fan.
You can then check if it needs to be cleaned i.e. dust build up etc or if it is faulty.
If faulty search online for ''Dell 15 5000 fan'' to find suppliers that suit you best.
Since you have to remove the heat sink, check the condition of the thermal paste that is covering the CPU under the heat sink. It may have dried out and will need refreshing. Dried out thermal paste can cause heating problems with the CPU. Here's the ifixit [guide|744] guide that may help.